1. Field of the Invention
The present invention relates generally to flexible circuits and methods for manufacturing such circuits, and more particularly to printed circuit board assemblies including optical fiber connectors and a flexible optical circuit. Even more specifically the present invention relates to the use of flexible optical circuits with strain relief arms. These arms assist in both mounting the flexible circuit to a circuit board or optical connector, and also in absorbing any forces acting on the flexible circuit thereby preventing damage to the optical fibers.
2. Brief Description of Earlier Developments
Many present day telecommunications systems, computer systems, etc. transmit and/or process both electrical signals and optical signals. Typically, optical signals are routed via optical fibers over relatively long distances in order to increase the transmission speed and efficiency relative to the propagation of electrical signals. In contrast, much of the signal processing analysis and storage is performed electrically. Thus, these systems must frequently convert optical signals to electrical signals, and electrical signals to optical signals.
Many of these systems, include a number of printed circuit boards or cards which plug into a back plane or mother board. The back plane generally provides power as well as a reference voltage or ground to each of the printed circuit boards. In addition, the back plane provides a pathway by which the printed circuit boards communicate with each other.
These types of circuit assemblies include optical connectors and flexible optical circuits which are secured optically via optical fibers to the optical connectors. Quite often either an optical disconnect and resulting data loss occurs in the system or even total failure of the optical system occurs due to a sudden strain type force (i.e. something that snags or pulls on the flexible circuit). It is a primary and specific advantage of the present invention to define a flexible optical circuit, method of manufacturing such a circuit and printed circuit assembly employing the flexible optical circuit, which includes a strain relief feature to avoid this type of optical disconnect issue.
Examples of some references which describe technology in the similar technical areas of this application include U.S. Pat. No. 4,496,215 (a flexible fiber optic cable for connecting an optical transmitter to an optical sensor in an electronic assembly), U.S. Pat. No. 5,204,925 (a flexible optical circuit having tab portions where the optical fibers terminate), U.S. Pat. No. 5,259,051 (apparatus and method of making optical fibers) and U.S. Pat. No. 6,005,991 (printed circuit board assembly having a flexible optical circuit).
In accordance with one embodiment of the present invention a printed circuit board assembly is provided comprising: a printed circuit board; an optical fiber connector adapted to be secured to the board; and a length of a flexible optical circuit having a number of optical fibers therein, one end of the length of flexible circuit includes a tab element the end portion of which is secured to the connector, the end portion also including at least one flexible strain relief arm projecting therefrom, each arm adapted to be secured to the connector.
In accordance with another embodiment of the present invention a flexible optical circuit comprises: at least one optical connector; and a length of a flexible material having a number of optical fibers therein, one end portion of the length of flexible material including a tab element the end portion of which is secured to the connector, the end portion also including at least one flexible strain relief arm projecting therefrom, each arm adapted to be secured to the connector.
In accordance with another embodiment of the present invention a method of fabricating a flexible optical circuit comprises the steps of: providing a plurality of optical fibers extending between first and second end portions of a length of flexible material, the length of flexible material having at one end portion a flexible tab element in combination with at least one flexible strain relief arm; mounting an optical connector to the flexible tab, the connector adapted to be secured to the relief arm; and securing each of the relief arms to the connector.
In accordance with another embodiment of the present invention a flexible circuit, comprises: a flexible substrate having an edge; at least one conductive element extending through the flexible substrate and having an end at the edge of the flexible substrate to engage a connector; and at least one strain relief element adjacent the end of the conductive element to engage the connector or a substrate on which the connector is mounted; wherein the strain relief prevents dislocation of the conductive element from the connector.
In accordance with still another embodiment of the present invention a method of preventing dislocation of a flexible circuit from a connector, the flexible circuit having an area occupied by conductive elements and an area unoccupied by the conductive elements, the method comprises the steps of securing the occupied area of the flexible circuit to the connector; and securing the unoccupied area of the flexible circuit to the connector or to a substrate on which the connector mounts; wherein the unoccupied area of said flexible circuit prevents a strain acting on the flexible circuit from reaching the occupied area and from disclocating the flexible circuit from the connector.